Servo-clutch



Nov. 26, 1935.

E. E. WEMP SERVO CLUTCH Filed Dec. 22, 1933 2 Sheets-Sheet 2 INVENTOR. Elm Arr [7 MN- Wiw Patented Nov. 26, 1935 UNITED STATES sEavo-cw'ron Ernest E. Wemp, Detroit, Mich. g n 7 Application December 22, 1933,.Serial No. 703,512 g 13 Claims. (.01. 192-36) This invention 'relatesto a servo-clutch and particularly to a clutch for use in an automotive vehicle. More particularly, the invention is (11? rected' to the provision. of a clutch engaged by packing springs and arranged to be released by an operator,-but in which the operator is not required to compress-the packing springs for clutch disengagement but merely actuates certain control mechanism which brings into effect outside power, such as the torque of some of the parts for compressing the packing springs.

The object of the invention is to provide an improved clutch structured the type mentioned.

In the drawings: 15 Fig. 1 is a cross sectional view of a clutch structure made in accordance with the invention showing the same in engaged position.

Fig. 2 is a partial sectional view showing the parts in released position.

20 Fig. 3 is an end view partly in elevation and with parts cut away and with some parts shown in section.

Fig. 4, is a diagrammatic developed view of a- I cam control element. 5 The crank shaft of an engine is illustrated 'at I attached to which is a flywheel 2 which may con stitute a clutch driving member. A driven disc 35 a tubular extension l through which the shaft extends and the purpose of which will presently appear.

The clutch may be provided with a cover plate I! attached to .the,flywheel by cap screwsor the.

40 like and which has a ball race it on its inner periphery edge which may be formed by suitably plate may be a sheet metal stamping and such material does not afford a hardened ball race but 45 the clutch herein is so designed that the clutch.

lcover itself may be used as a ball race as willlater appear. j A pressure plate is shown at I! which may. be associated in-driving relation with the cover plate 50 by means of projections 18 slidably fitting in slots 19 in the cover plate. The pressure plate may be urged towards the driven disc by an annulus oi coil springs 20 arranged between the pressure 'plate -and coveri The Pressure plate may 55 have an axial extension 'l'i i'onthe purpose of associating the pressureplate with controlling means. v

The controlling means comprises an element or elements for exerting force on the pressure plate to retract it from the driven disc, thus 5 compressing the packing springs. For this purpose the axially extending portion 2i may be provided with a number of devices to which the force is applied and which devices advantageously take the iorm'oi rollers 25. Each roller may be journaled on a pin 26 through the means of a small or needle-type roller bearing 21. The outer end of each pin 26 may be reduced in cross section and fitted in the aperture'oi a spacing washer 28. The inner end may be ,reduced'in cross section and may be provided with a head 29.

A ring which may be a sheet metal stamping U- shape in cross section, and as illustrated at 30, may be slipped into place; the ring has notched portions as at 3| i'or fitting over the reduced part and the body portion of each pin, while the other leg of the U lies over ?the .outer end of each pin and the roller as shown. The ring may be held to the pressure plate by one or more screws 32.

Preferably there are three rollers. In making the assembly each pin 26 may be inserted from the interior of the extension 2| and its outer end passed into the roller and washer 28; then the ring 30 may be positioned by axial movement from the rear'and it embraces each pin so it is 30 prevented from displacement. As clearly shown inFig. 1 each pin is held from axial'movement.

The retracting or servo-devicemay advantageously take theiorm of a sheet metal stamping generally Z-shaped in cross section having an intermediate portion 35 and end'portions 36 and 31. The intermediate portion may substantially parallel the'axis and the endportions maybe substantially perpendicular" thereto. The outer portion :1 maybe provided with .suitable'iric 40' tion facing material as at v38. Anti-friction eleshaping the metal of the cover plate. .The cover menta-sdchas balls'l9,-"may be disposed'between the race It on the cover plate and the angle between the parts Stand 31 oi'rthe servo-device which forms-another race. "Ajtorsion 'pring 4045 has oneien'd connect'ed to the servo-deviceas shown at, and the other connectednto the cover plate as by-imean'soi the stud42.

- The portion 36 is provided with inclined planes or cam elements i'or' cooperation with the rollers" 2.5., This may be accomplished by a suitable shaping. of the flange 36 asillustrated in Fig. 4." Y

The developed view 4) is' reduced insize,

elements 45 connected by relatively abrupt portions 46. Since it is advantageous to use a three point contact between the servo-device and the pressure plate, three rollers are provided and three cams are provided.

A control plate 41 has a hub portion slidably mounted upon the extension ill but keyed thereto as at 48 so that it cannot rotate. It may be held retracted by a spring 49 fastened to the control plate and to a clip 50. 'The control plate may of rotation relative to the cover plate and pressure ring. The torsion spring 40 serves to properly position the servo-ring under normal driving conditions. The parts may rotate in the usual manner which may be counter-clockwise as Fig.

1' is viewed from the right and counter-clockwise.

as Fig. 3 is viewed. An advantageous arrangement is to have the torsion spring hold the servo ring in a position where the several rollers contact with the abrupt portions 4fi'as illustrated at positions a of Fig. 4, the rollers being shown in solid lines. As a result the servo-ring is cammed forwardly with a fairly light pressure thus holding the anti-friction balls tightly engaged between the cover plate and the servo-ring and, as well, holding the servo-ring and rollers in snug engagement to the end that there is no looseness.

To disengage the clutch an operator depresses the lever 54 to bring the control plate into frictional engagement with the facing l8 and thus decelerate the servo-ring. The rollers and servering move relative to each other, and when the rollers come to position b as illustrated in dotted lines, they strike the cams 45 and upon continued movement the rollers ride upthe cams to position c, thus shifting the pressure plate against the action of the springs 20 and releasing the clutch. When the clutch is disengaged the servo-ring again rotates uniformly with the driving members, and to accomplish this the relative rotational movement may be limited by a more or less central part 60 of the pressure ring making contact with the servo-ring as illustrated at a: in Fig.

2. At this time, of course, there is friction between the facing 38 and the control plate 41 and the clutch is held disengaged so long as the operator maintains sufficient friction. To. engage the clutch the operator merely releases the pedal slowly or quickly as desired to get a gradual or quick clutch engagement; this releases the servoring and the torsion spring returns it to its normal position. clutch becomes fully engaged when the rollers reach position b of Fig. 4, and then the servoring continues to move until the rollers and cams are in the relative positions as illustrated at a.

The slight retracting force on the pressure ring in normal position is not sufllcient to have any 'detrimental effect upon the clutch 'as the packing springs 20 are so much stronger than the torsion spring 40.

less than, the weight of the operator's foot, and

On the return movement the In the reengagement of the clutch the forward motion of the pressure plate resulting in the rollers'25 acting upon the cams by varying the amount of pressure the clutch action may be controlled with a nicety. The particular design herein affords a large diameter for the cam elements or inclined planes with the result that the cams may be relatively long and a large mechanical advantage may be obtained. Also, a bearing "of large diameter is provided by the anti-friction elements between the cover plate and servo-ring and it is thought to be preferable to provide a large number of anti-friction 10 elements or balls in this bearing. Due to the large diameter thus provided and the use of a large number of anti-friction elements it is feasible to have the ball races formed by suitably shaped portions of the cover plate and servo-ring. Another feature of the design is the rigidity and strength of the structure although the same may be parts made from sheet metal stampings. The reaction points are kept close together. 'That is to say, the point where the cams take the clutch releasing force is not far removed radially from'the bearing 38. Moreover the reaction force on the race It of the cover plate is positioned relatively close to the point of attachment of the cover plate tothe flywheel.

I Accordingly, there is very little distortion of these structure eliminates the usual clutch levers by means of which a mechanical'advantage is obtained in releasing the clutch. As is well known to those versed in the clutch art a number of these levers extend radially from a point near the center of the clutch outwardly and they require a certain amount of. space which in turn makes itnecessary to reduce the number of packing springs. However,in the clutch herein disclosed the space for the packing springs is not 40 interfered with and as a result a large number of springs may beused, and each spring accordingly may be of less strength than each spring in an assembly where fewer springs are used, yet

obtaining a clutch of requisite. torque capacity.

I claim:

1. A clutch comprising in combination, a driving member, another driving member in the form of an axially shiftable pressure plate and having a driving connection with the first driving memher, a driven member arranged to be packed between the driving members when the clutch is engaged, an annulus of packing springs acting directly upon the pressure plate to engage the clutch, a servo-device normally rotating in uni- 56 son with the pressure plate and having a positively limited rotationalmovement relative to the pressure plate and held in a fixed axial position, inclined planes on the servo-device, means on inclined planes, and operatorcontrolled means i'or'causing such relative rotational movement of the servo-device whereby the inclined planes act directly upon the pressure plate to shift the same axially against the action of the springs to dis- 6 engage the clutch.

2. A clutch comprising, driving and driven members arranged to be packed together in driving relation and including an axially shiftable pressure plate, a clutch cover plate, a servo-device associated [with the cover plate and normally rotating in unison therewith and having a limited rotationalmovement relative thereto, anti-friction bearing elements between the cover plate and the servo-device, inclined planes. on the servodevice, abutmentmeans on the pressure plate for direct operation on the inclined planes, and operator'controlled friction means for decelerating the servo-device to 5 cause 1 suchlimited relative rotational movement of the servo-device.

'3. A clutch comprising in combination; driving shiftable pressure platefia' clutchcovefplate, said plate being-formed with a bearing race,- -a servodevice associatedwith'the cover plate and also formed with a" bearing race, anti'-friction elements between the two races,"- said servo-device being arranged to normally rotatein unison with the cover-plate. but capable of limited rotational 1 movement relative thereto, inclined planes on the servo-device, abutmentmeans on the pressure plate-for'coope'ration with the inclined planes, and operator controlled means for applyingv friction to the servo-devlce'to cause-such limited rel ative rotational movement of the servo-device.

' plate and having a bearing race directly therein,

'4. A clutch comprising'in combination, driving and driven members arranged to be packed together indriving relation and including an axially shiftable pressure plate, a clutch cover plate comprising a sheet metal stamping formed with a bearing race directly therein, a servo-device of sheet me'tal'sta'mping associated with the cover a plurality of closely spaced anti-friction balls 7 betweenthe races, said servo-device normally rotating inunison" with the cover plate but capable oflimited rotational movement relative thereto, inclinedpla'nes on the servo-devic'e, means by which the inclined planes are effective upon the pressure plate; and operatotr controlledmeans for causing such limited relative rotational movement of the servo-device.

51A clutch comprising, a driving member, another drivin'g" member in theform of anax'ially shiftable pressure-plate, a driven member and a driven shaft'thereforfa clutch cover plate fastened to the flrst'driving member andextending axially over the pressure plateand'havlng a radially'inwardly extending part, an annulus of clutch packing springs j between theinwardly extending part of the co'verplate and the pressure plate, the inwardly Qextending p'art {of the c over plate *"havingi aicentral aperture; therein of relatively great *diam'etena's cc'imp'ared' to the driven shaft, and the peripneral 4 portion of the cover" plate around the aperture 'being formed into bea'iring race,the-pressure plate having an axialaextension in said aperture of the r 7 cover plate,- abutmen t means on said extension, a servoedevice having. an: axiallyextending portion "extending through the aperture randatelescoping over; the .said1 extension; and, having a bea in a e,ant 1irict ie e nent e weem said two bearing races, the inner -pqrtion of, the

" servoedevicehaving, a;,radially inwardly extending-part overlapping "the said abutments and provided with inclined planes, spring means interconnecting the cover plate and servo-device holding the servo-device to normally rotate in unison shiftable pressure plate. a driven member and a driven shaft therefor, .a clutch cover plate fastened to the first driving member and extending axially over the pressure, plate and having a radially inwardly extending part, an annulus of clutch packing springs between the inwardly extendin part of the cover plate and the pressure plate, the inwardly extending part of the cover plate having a central aperture therein of relatively great diameter as compared to the driven 1 shaft, and the peripheral portion of the-cover plate around the aperture having a bearing race, the pressure plate having an axial extension in saidaperture of the cover plate, abutment means on said extension, a servo-device having an axial- 1 1y extending portion extending through the aperture and telescoping over the said extension and having a bearing race, anti-friction elements between the said two bearing races, the inner portion of the servo-device having a radially inward- 2 ly extending part overlapping the said abutments and provided with inclined planes, spring means interconnecting the cover plate and servo-device holding the servo-device to normally rotate in unison with the cover plate, said servo-device 2 having limited rotational movement relative to the cover plate, and operator controlled means for applying friction to the servo-deviceto decelerate same to cause such limited relative rotational movement thereof, whereby the in- 8' clined planes act upon the said abutments to shift the pressure plate axially and release the clutch.

7. A clutch comprisinga driving member, an-

other driving member in the form of an axially I3- shiftable pressure plate, a driven member and a driven shaft therefor, a clutch cover plate fastened to the first driving member and extending axlaliy over the pressure plate and having a radially inwardly extending part, an annulus of 4 clutch packing springs between the inwardly extending part of the cover plate and the pressure plate, the inwardly extending part of the cover plate having a central aperture therein of relatively great diameter as compared to the driven i shaft, and the peripheral portion of the cover unison with the cover plate, said servo-device having limited rotational movement relative to the cover plate, the outer portion of the servodevice extending in a radial direction, a nonrotatable control plate, and means for shifting the plate into frictional engagement with the last mentioned portion of the servo-device to decelerate the same and cause such limited rotational movement thereof whereby the inclined planes act upon said abutments to release the clutch.

8. In a servo-clutch, a clutch cover plate having an aperture therein, a clutch pressure plate formed with abutments, a substantially Z-shaped servo-device journaled in the aperture of the cover plate, the inner portion of which has in- 7 mally rotatable in unison with the cover plate, said servo-device having limited rotational move.-

ment relative to the cover plate against the action of said spring, and a non-rotatable operator actuated control plate movable into frictional engagement with the outer portion of the servodevice to decelerate the same and cause such limited relatively rotational movement against the action of said spring whereby the inclined planes act upon the abutments and shift the pressure plate to release the clutch, said spring returning the servo-device to its initial position when the same is released by the control plate.

9. In a servo-clutch, a clutch coverplate having a central aperture therein, a pressure plate having an extension concentric with the aperture, abutment means on the extension, a servoring journaled in the aperture and substantially Z-shape in cross section, cam surfaces on the inner leg of the Z cooperating with the abutments,

spring means connecting the cover plate and servo-ring, said servo-ring normally rotating with the cover plate, an operator controlled friction means arranged to be brought in frictional engagement with the outer leg of the Z to cause the servo-ring to decelerate relative to the cover plate whereby the cam surfaces act upon the abutments and shift the pressure plate, and means for limiting the decelerating movement of the servo-ring.

10. In a servo-clutch, an axially shiftable pres-, sure ring, a cover plate having an aperture, clutch the decelerating movement of the servo-device,

bearing means between the cover plate and the servo-device fortaking the reactive force of the packing springs, said bearing means and the cam surfaces being located within the inner and outer peripheries of the pressure ring.

11. In a servo-clutch, a driving member, a clutch cover plate fastened thereto, a clutch pressure plate having abutments thereon, a servodevice arranged to normally rotate in unison with the cover plate and having cam surfaces for acting upon the said abutments, packing springs between the cover plate and the pressure plate, op-

' erator controlled means for shifting the servodevice rotationally relative to the cover plate whereby the cam elements act upon the said abutclined planes for cooperation with the abutments, spring means interconnecting the cover plate and servo-device so that the servo-device is held norments and shift the pressure plate,.bearing means between the servo-device andv the cover plate for taking the reactive force of the packing springs, said bearing means being located relatively close! to the point of attachment of the cover plate to; the driving member tominimize distortion of the pressure plate, and-said bearing means and the place of contact between the cams and abutments being positioned relatively close to each other to minimize distortion in the servo-device. 1o

12. In a servo-clutch. a pressure plate having abutments thereon, a cover plate, a servo-device, said servo-device having circumferentially arranged cam elements one for operating on each abutment-with said cam elements connected by 15 relatively abrupt parts, packing springs between the cover plate and pressure plate, said servodevice journaled on the cover plate for limited rotation relative thereto, spring means interconnecting the cover plate and servo-device normally holding the servo-device in a position where the abruptparts contact with the abutments and hold the servo-device and cover plate tightly together by the reaction of the packing springs, and operator controlledv means for causingthe servodevice to move rotationally relative to the cover plate whereby the cam elements act upon the abutments to shift the pressure plate, said spring which interconnects the servo-device and cover plate serving to return the servo-device to a position where the abruptparts again contact with the abutments upon release of the servodevice of'the operator controlled means.

13. A servo-clutch comprising, a flywheel, a cover plate secured thereto, a pressure plate, an annulus of coil springs between the cover plate and pressure plate, a driven disc between the flywheel and pressure plate and packed between these two members by said springs, interengaging means between the pressure plate and the cover 40 plate, establishing a driving connection therebetween and arranged to permit the pressure plate to shift axially with respect to the cover plate, said cover plate having a central aperture therein inside the annulus of springs. the pressure plate having parts extending axially through said 

